Spinal interbody spacer

ABSTRACT

A spinal spacer for engagement between vertebrae includes a body extending between a substantially contoured first end surface and a second end surface to define side surfaces and opposing top and bottom vertebral engaging surfaces substantially symmetrical about a centerline axis. At least one opening defines a hollow inner body and includes first and second intersecting openings extending through the top and bottom vertebral engaging surfaces. The second intersecting opening extends through the side surfaces. The second end surface includes at least one aperture formed therethrough in communication with the hollow inner body. A screw opening is defined through at least one plate insert configured to be removably coupled to the second end surface to substantially align the screw opening with the at least one aperture. The bone screw is configured to be threadingly secured within the at least one plate insert.

BACKGROUND

1. Technical Field

The present disclosure relates to devices for implantation betweenadjacent vertebrae. Specifically, the disclosure relates to a spinalinterbody spacer that inhibits the collapse of the space betweenadjacent vertebrae after a discectomy.

2. Background of Related Art

After a partial or complete discectomy, the normally occupied spacebetween adjacent vertebral bodies is subject to collapse and/ormisalignment due to the absence of all or a part of the intervertebraldisc. In such situations, the physician may insert one or moreprosthetic spacers between the affected vertebrae to maintain normaldisc spacing and/or the normal amount of lordosis in the affectedregion.

Typically, a prosthetic implant is inserted between the adjacentvertebrae and may include pathways that permit bone growth between theadjacent vertebrae until they are fused together. However, there existsa possibility that conventional prosthetic implants may be dislodged ormoved from their desired implantation location due to movement by thepatient before sufficient bone growth has occurred.

Therefore, a need exists for a spinal implant that provides a desiredamount of lordosis, allows for bone growth between adjacent vertebrae,maintains the space between adjacent vertebrae during bone ingrowth, andresists dislocation from its implantation site.

SUMMARY

According to one embodiment of the present disclosure, a spinal spacerfor engagement between vertebrae includes a body having a first endsurface at a distal end of the body and a second end surface oppositethereto at a proximal end of the body. The body extends between thefirst and second end surfaces to define opposing top and bottomvertebral engaging surfaces substantially symmetrical about a centerlineaxis. The body further defines side surfaces. A hollow inner body isdefined by an opening extending through the top and bottom vertebralengaging surfaces. The second end surface of the body includes at leastone aperture formed therethrough at an angle relative to the centerlineaxis and in communication with the hollow inner body. At least one plateinsert has a screw opening defined therethrough and is configured to bemounted to the body with the screw opening substantially aligned withthe at least one aperture. The plate insert is configured with a lipdisposed in the screw opening configured to engage threads of a bonescrew to secure the bone screw within the at least one plate insert.

According to another embodiment of the present disclosure, a spinalspacer for engagement between vertebrae includes a body having a firstend surface at a distal end of the body and a second end surfaceopposite thereto at a proximal end of the body. The body extends betweenthe first and second end surfaces to define opposing top and bottomsurfaces. The body further defines side surfaces and a hollow opencentral region extending through the top and bottom vertebral engagingsurfaces. The second end surface of the body includes at least oneaperture formed therethrough at an angle relative to a centerline axisextending between the proximal and distal surfaces. The at least oneaperture has a screw opening defined therethrough. The at least onescrew opening has formed therein a lip configured and dimensioned toengage threads on the head of a screw inserted through the at least oneaperture.

According to yet another embodiment of the present disclosure, a spinalspacer for engagement between vertebrae includes a body having a firstend surface at a distal end of the body and a second end surfaceopposite thereto at a proximal end of the body. The body extends betweenthe first and second end surfaces to define opposing top and bottomsurfaces. The body further defines side surfaces and a hollow opencentral region extending through the top and bottom vertebral engagingsurfaces. The second end surface of the body includes at least oneaperture formed therethrough at an angle relative to a centerline axisextending between the proximal and distal surfaces. The at least oneaperture has a screw opening defined therethrough and the body furtherincludes a plate cavity. At least one plate insert has a plate screwopening defined therethrough and is configured and dimensioned to beinserted into the plate cavity with the plate screw opening aligned withthe body screw opening. The plate screw opening includes a lipconfigured to engage a bone screw.

The present disclosure also provides for a method of fusing adjacentvertebrae. The method includes inserting a spinal spacer between thesurfaces of the adjacent vertebrae. The spinal spacer extends between afirst end surface at a distal end and a second end surface at a proximalend to define opposing top and bottom surfaces substantially symmetricalabout a centerline axis. The second end surface has at least one angledaperture defined therethrough and at least one corresponding plateinsert having a screw opening configured to substantially align with theat least one angled aperture. The method also includes advancing a bonescrew through a first angled aperture defined through the second endsurface of the spinal spacer at a first angle relative to the centerlineaxis and into the vertebrae until the bone screw engages bone andthreads on the head of the bone screw engage the at least one plateinsert to secure the bone screw relative to the spinal spacer.

According to another embodiment of the present disclosure, a method offusing adjacent vertebrae includes inserting a spinal spacer between thesurfaces of the adjacent vertebrae. The spinal spacer extends between afirst end surface at a distal end and a second end surface at a proximalend to define opposing top and bottom surfaces substantially symmetricalabout a centerline axis. The second end surface of the body includes atleast one aperture formed therethrough at an angle relative to acenterline axis extending between the proximal and distal surfaces. Theat least one aperture has a screw opening defined therethrough. Themethod also includes advancing the bone screw through a first aperturedefined through the second end surface of the spinal spacer at a firstangle relative to the centerline axis and into the vertebrae until thebone screw engages bone and threads on the head of the bone screwengages the at least one screw opening to secure the bone screw relativeto the spinal spacer.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the presently disclosed spinal interbody spacer aredescribed herein with reference to the accompanying drawings, wherein:

FIG. 1 is a perspective view generally from a leading or distal end ofan embodiment of a spinal interbody spacer according to the presentdisclosure, shown assembled with bone screws;

FIG. 2 is a side view of the spinal interbody spacer of FIG. 1;

FIG. 3 is top plan view of the spinal interbody spacer of FIG. 1 showinga vertebral-engaging surface;

FIG. 4 is a rear elevational view of the trailing or proximal end of thespinal interbody spacer of FIG. 1;

FIG. 5 is an exploded rear elevational view of the trailing or proximalend of the spinal interbody spacer of FIG. 1 with parts separated;

FIG. 6 is a rear elevational view of a trailing or proximal end of aspinal interbody spacer according to an embodiment of the presentdisclosure;

FIGS. 7A and 7B are side views of a bone screw for use with the spinalinterbody spacers of FIGS. 1 and 6 according to an embodiment of thepresent disclosure;

FIGS. 8A and 8B are side views of a bone screw for use with the spinalinterbody spacers of FIGS. 1 and 6 according to another embodiment ofthe present disclosure;

FIGS. 9A and 9B are side views of a bone screw for use with the spinalinterbody spacers of FIGS. 1 and 6 according to another embodiment ofthe present disclosure; and

FIGS. 10A and 10B are side views of a bone screw for use with the spinalinterbody spacers of FIGS. 1 and 6 according to another embodiment ofthe present disclosure.

DETAILED DESCRIPTION

Embodiments of the presently disclosed spinal interbody spacer will nowbe described in detail with reference to the drawings, in which likereference numerals designate identical or corresponding elements in eachof the several views.

In the drawings and in the description that follows, the term proximalrefers to the portion of the device that is closest to the operator,while the term distal refers to the portion of the device that isfurthest from the operator. Additionally, in the drawings and in thedescription that follows, terms such as front, rear, upper, lower, top,bottom, and the similar directional terms are used simply forconvenience of description and are not intended to limit the disclosureattached hereto.

Referring now to FIGS. 1-5, there is disclosed an embodiment of a spinalinterbody spacer 100 for engagement between vertebrae according to thepresent disclosure. More particularly, referring to FIGS. 1-3, spinalinterbody spacer 100 includes a body 102 having a substantiallycontoured first end surface 104 at a distal or leading end 106 of thebody 102 and a second end surface 108 opposite thereto at a proximal ortrailing end 110 of the body 102. The body 102 extends between the firstand second end surfaces 104 and 108 to define respective top and bottomvertebral engaging surfaces 112 a, 112 b, as well as opposed sidesurfaces 162 a, 162 b. The top and bottom vertebral engaging surfaces112 a, 112 b are disposed opposite to one another.

As best illustrated in FIGS. 1 and 2, the body 102 is configured suchthat the top and bottom vertebral engaging surfaces 112 a, 112 bintersect the side surfaces 162 a, 162 b, respectively, to provide asubstantially quadrilateral cross-section with rounded corners 140. Asillustrated in FIGS. 1-5, the body 102 has, by way of example, asubstantially rectangular cross-section, although other quadrilateralshapes such as a square are also contemplated. In addition, thecross-section shape may also be hexagonal or other suitable multilateralshape. The embodiments are not limited in this context.

As best illustrated in FIG. 2, the body 102 is also configured such thatthe top and bottom vertebral engaging surfaces 112 a, 112 b have asubstantially streamlined convex profile, and are configured to besubstantially symmetrical around a centerline axis X-X that extends fromthe distal end 106 to the proximal end 110. As best illustrated in FIGS.1 and 3, the body 102 is configured such that the side surfaces 162 a,162 b have a substantially atraumatic blunt nose profile with respect tothe contoured first end surface 104 and the substantially flat or planarsecond end surface 108. The intersection of the top and bottom surfaces112 a, 112 b of the nose portion with the side surfaces 162 a, 162 b ofthe nose may be rounded to enhance the atraumatic character of the nose.

FIG. 3 illustrates a plan view of the top vertebral engaging surface 112a. As illustrated in FIGS. 1-3, surfaces 112 a, 112 b each have aplurality of protrusions 122 having a particular configuration. Theplurality of protrusions 122 define a set of grooves 124 that facetowards the proximal end 110. Each groove of the set of grooves 124 hasa position along the top and bottom vertebral engaging surfaces 112 a,112 b. Each groove of the set of grooves 124 includes a first face 126that is substantially orthogonal to the top and bottom vertebralengaging surfaces 112 a, 112 b, i.e., to the axis X-X, at the respectiveposition of the groove. Each groove of the set of grooves 124 includes asecond opposing face 128. As best shown in FIG. 1, the second face 128is substantially sloped or inclined with respect to the top and bottomvertebral engaging surfaces 112 a, 112 b so that the surfaces 126, 128converge at the bottom of the groove. The surfaces 126, 128 may directlyintersect as shown or a further surface feature, such as a flat surfaceportion substantially parallel to axis X-X may extend between andconnect surfaces 126, 128.

Referring to FIG. 2, it can be seen that the side surfaces 162 a, 162 bare slightly arcuate such that the apex of the arc thereof has a greaterheight than both the first and second end surfaces 104 and 108,respectively. As such, the body 102 has a maximum height dimension A asmeasured by the distance between the tip of a protrusion 122 a on thetop vertebral engaging surface 112 a distanced from the proximal end 110and the tip of a protrusion 122 b on the bottom vertebral engagingsurface 112 b correspondingly distanced from the proximal end 110.

Referring again to FIGS. 1 and 2, the body 102 may further include anaperture 130 formed therein that extends transversely across the body102 through the side surfaces 162 a, 162 b. The aperture 130 may bedisposed transversely under at least a portion of the top vertebralengaging surface 112 a and over at least a portion of the bottomvertebral engaging surface 112 b.

Referring again to FIGS. 1 and 3, the body 102 may further include anaperture 132 formed therein that may extend vertically through the body102. The paths of the apertures 130, 132 intersect to form a hollowcentral region 134 (FIG. 3) of the body 102. The apertures 130, 132 andthe hollow central region 134 may be filled with osteoconductive orosteoinductive materials (e.g. bone, bone chips, bone substitutes, bonegrowth promoting materials such as bone morphogenic proteins, etc.), orboth, to enable and/or promote growth of vertebral bone therebetween topromote fusion of the adjacent spine segments and/or anchor the spinalinterbody spacer 100 within the spine of a patient.

As best shown in FIG. 3, the top vertebral engaging surface 112 aincludes at least one aperture 195 formed therein and at least partiallypenetrating therethrough configured to receive an optional fiduciaryinsert (not shown), thus allowing the orientation of the spinalinterbody spacer 100 to be determined using a number of differentimaging modalities as are known in the art. This feature is particularlyimportant when spacer 100 is made from a substantially radiolucentmaterial (e.g. polyetheretherketone or PEEK). In embodiments, top andbottom vertebral engaging surfaces 112 a, 112 b may include additionalapertures (not shown) at least partially penetrating therethrough tocomplement aperture 195.

Referring to FIGS. 4 and 5, the proximal end 110 of the body 102 furtherincludes a plurality of angled apertures disposed through the second endsurface 108 communicating with the hollow central region 134. In theillustrated embodiment, three apertures are disposed through the secondend surface 108, including one aperture 150 angled in a first direction,and two apertures 152 and 154 having a corresponding degree of angle ina second direction. In use of the spinal interbody spacer 100, the body102 may be inverted such that aperture 150 is angled in the seconddirection and apertures 152, 154 are angled in the first direction. Eachof angled apertures 150, 152, 154 are adapted to receive a bone screw155 therethrough for insertion into bone, as will be discussed infurther detail below.

Referring to FIGS. 4 and 5, the proximal end 110 of the body 102 furtherincludes a plurality of insert slots 150 a, 152 a, 154 a defined in thesecond end surface 108 communicating with angled apertures 150, 152,154, respectively. As shown in FIG. 5, each of slots 150 a, 152 a, 154 aare configured and dimensioned to slidably receive a respective plateinsert 190, 192, 194 therein. Each of plate inserts 190, 192, 194includes a respective screw opening 190 a, 192 a, 194 a definedtherethrough and an annular sidewall extending downward from a topsurface of plate inserts 190, 192, 194 to form a corresponding lip 190b, 192 b, 194 b proximate a bottom surface thereof. When plate inserts190, 192, 194 are inserted within slots 150 a, 152 a, 154 a, screwopenings 190 a, 192 a, 194 a substantially align with correspondingapertures 150, 152, and 154 or are otherwise coincident therewith topermit the bone screw 155 to be advanced therethrough. As bone screw 155is advanced through any one of apertures 150, 152, 154 to communicatewith hollow central region 134, bone screw 155 threadingly engages lips190 b, 192 b, 194 b to retain bone screw 155 within plate inserts 190,192, 194, as will be discussed in further detail below. Plate inserts190, 192, 194 are constructed of medical grade titanium. Further, thesurface of plate inserts 190, 192, 194 may be anodized to provide aporous coating for absorbing a colored dye and/or to provide corrosionresistance.

Referring now to FIG. 6, a spinal interbody spacer 200 is shownaccording to another embodiment of the present disclosure. Spinalinterbody spacer 200 is substantially as described above with respect tospacer 100 but includes features distinct from spacer 100 which will bediscussed in detail below. Spacer 200 is constructed of medical gradetitanium. Further, the surface of spacer 200 may be anodized to providea porous coating for absorbing a colored dye and/or to provide corrosionresistance. As with spacer 100, spacer 200 includes a body 202 extendingbetween a first end surface 204 and a second end surface 208 to definerespective top and bottom vertebral engaging surfaces 212 a, 212 b, aswell as opposed side surfaces 262 a, 262 b. An aperture 230 through theside surfaces 262 a, 262 b extends transversely across the body 202 tointersect an aperture 232 extending vertically through body 202 to forma hollow central region 234. These elements function substantially asdescribed above with respect to spacer 100 and will not be discussed infurther detail herein.

Body 202 further includes a plurality of angled apertures 250, 252, 254disposed through the second end surface 208 communicating with thehollow central region 234. In the illustrated embodiment, threeapertures 250, 252, 254 are disposed through the second end surface 208,including one aperture 250 angled in a first direction, and twoapertures 252 and 254 having a corresponding degree of angle in a seconddirection. Each of angled apertures 250, 252, 254 are adapted to receivea bone screw 155 therethrough for insertion into bone, as will bediscussed in further detail below. Each angled aperture 250, 252, 254includes an annular sidewall extending outward from a side surfacethereof to form a corresponding lip 250 a, 252 a, 254 a proximate abottom surface of each angled aperture 250, 252, 254 and distal a topsurface of each angled aperture 250, 252, 254. As a bone screw isadvanced through any one of apertures 250, 252, 254 to communicate withhollow central region 234, the bone screw threadingly engages lips 250a, 252 a, 254 a to retain the bone screw within apertures 250, 252, 254,as will be discussed in further detail below.

Referring now to FIGS. 7A and 7B, one embodiment of bone screw is shownreferenced generally as 155. As described herein, bone screw 155 isconfigured for use with spinal interbody spacer 100 and/or spinalinterbody spacer 200. Bone screw 155 includes a shank 170, a taperedhead portion 174 at a proximal end of the shank 170, and a pointed tipportion 176 at a distal end of the shank 170. The shank 170 has auniform outer diameter and a first continuous helical thread 170 aformed thereon for threaded insertion into bone. A second continuoushelical thread 174 a is formed on the head portion 174 for engaging thelip of the corresponding screw openings 190 a, 192 a, 194 a. The pitchof the first thread 170 a is greater than the pitch of the second thread174 a. Each of the first and second threads 170 a, 174 a has asubstantially uniform pitch.

Bone screw 155 further includes a self-starting portion 180 that extendsproximally from the pointed tip portion 176. The self-starting portion180 includes first and second sidewalls 182, 184 that define a flutesection 186. As best shown in FIG. 7B by way of example, the first andsecond sidewalls 182, 184 of the flute section 186 extend from thepointed tip portion 176 to a crest 185 of thread 170 a near the distalend of shank 170. The first sidewall 182 is planar and is aligned alonga central longitudinal axis X′-X′ of the bone screw 155 such that firstsidewall 182 is coplanar with the central longitudinal axis X′-X′. Asbest shown in FIG. 7A by way of example, the second sidewall 184 furtherincludes a planar portion 184 a that is parallel to the centrallongitudinal axis X′-X′ and an arcuate portion 184 b that extendsproximally from the planar portion 184 a. The arcuate portion 184 b iscut along a radius of curvature, as shown in FIG. 7A. Preferably, bonescrews 155 are constructed of a material which is harder than thematerial of plate inserts 190, 192, 194 (FIG. 5) and/or lips 250 a, 252a, 254 a (FIG. 6). For example, the bone screw may be made of titaniumalloy (e.g., Ti-6Al-4V) with the plate inserts and/or lips made of asofter compatible material, such as a softer titanium material.

In use with spacer 100, bone screw 155 is advanced (i.e., rotatedclock-wise) through apertures 150, 152, 154 toward hollow central region134 such that self-starting portion 180 engages vertebral bone tothreadingly advance thread 170 a of shank 170 therein. Since thetitanium makeup of plate inserts 190, 192, 194 is softer than thetitanium alloy makeup of the bone screw 155, as bone screw 155 isadvanced through any one of apertures 150, 152, 154 toward hollowcentral region 134, thread 174 a of head portion 174 engages thecorresponding lip 190 b, 192 b or 194 b to deform the lip and securebone screw 155 in the corresponding screw opening 190 a, 192 a or 194 asuch that bone screw 155 resists backing out of the screw opening.Further, head portion 174 of bone screw 155 is dimensioned to engagelips 190 b, 192 b, 194 b to prevent further advancement of bone screw155 toward hollow central region 134. This type of screw lockingarrangement is disclosed and shown in U.S. Pat. No. 6,322,562 to Wolter,the entire contents of which are hereby incorporated by reference as ifrepeated herein.

With reference to use with spacer 200, the titanium makeup of lips 250a, 252 a, 254 a is softer than the titanium alloy makeup of the bonescrew 155, as bone screw 155 is advanced through any one of apertures250, 252, 254 toward hollow central region 234, thread 174 a of headportion 174 engages the corresponding lip 150 a, 152 a, or 154 a todeform the lip and secure bone screw 155 in the corresponding aperture150, 152, 154 such that bone screw 155 resists backing out of theaperture. Further, head portion 174 of bone screw 155 is dimensioned toengage lips 150 a, 152 a, or 154 a to prevent further advancement ofbone screw 155 toward hollow central region 234.

Referring now to FIGS. 8A and 8B, another embodiment of a bone screw isshown referenced generally as 255. As described above with reference tobone screw 155, bone screw 255 is configured for use with spinalinterbody spacer 100 and/or spinal interbody spacer 200 in the samemanner as described hereinabove. Bone screw 255 includes a shank 270, atapered head portion 174 at a proximal end of the shank 270, and arounded tip portion 276 at a distal end of the shank 270. The shank 270has a uniform outer diameter and a first continuous helical thread 270 aformed thereon for threaded insertion into bone. A second continuoushelical thread 274 a is formed on the head portion 274 for engaging lips190 b, 192 b, 194 b (FIG. 5) or lips 150 a, 152 a, 154 a (FIG. 6). Thepitch of the first thread 270 a is greater than the pitch of the secondthread 274 a. Each of the threads 270 a, 274 a has a substantiallyuniform pitch.

Bone screw 255 further includes a self-tapping portion 280 that extendsproximally from the rounded tip portion 276. The self-tapping portion280 includes first and second sidewalls 282, 284 that define a flutesection 286. The first and second sidewalls 282, 284 of the flutesection 286 extend from the rounded tip portion 276 to a crest 285 ofthread 270 a near the distal end of shank 270. The first sidewall 282 isplanar and is parallel to a central longitudinal axis X″-X″ of the bonescrew 255 such that first sidewall 282 is offset from the centrallongitudinal axis X″-X″. As best shown in FIG. 8A by way of example, thesecond sidewall 284 further includes a planar portion 284 a that isparallel to the central longitudinal axis X″-X″ and an arcuate portion284 b that extends proximally from the planar portion 284 a. The arcuateportion 284 b is cut along a radius of curvature, as shown in FIG. 8A.Preferably, bone screws 255 are constructed of a material which isharder than the material of plate inserts 190 b, 192 b or 194 b (FIG. 5)and/or lips 150 a, 152 a, 154 a (FIG. 6). For example, the bone screwsmay be made of titanium alloy (e.g., Ti-6Al-4V) with the plate insertsand/or lips made of a softer compatible material, such as a softertitanium material.

Referring now to FIGS. 9A and 9B, another embodiment of bone screw isshown referenced generally as 355. As described above with reference tobone screw 155, bone screw 355 is configured for use with spinalinterbody spacer 100 and/or spinal interbody spacer 200 in the samemanner as described hereinabove. Bone screw 355 includes a shank 370, aneck portion 375 extending between the shank 370 and a flange portion390 disposed at a proximal end of neck portion 375, an independenttapered head portion 374, and a pointed tip portion 376 at a distal endof the shank 370. The shank 370 has a uniform outer diameter and a firstcontinuous helical thread 370 a formed thereon for threaded insertioninto bone. A second continuous helical thread 374 a is formed on theindependent head portion for engaging lips 190 b, 192 b, 194 b (FIG. 5)or lips 150 a, 152 a, 154 a (FIG. 6) of spacers 100 and 200respectively. The pitch of the first thread 370 a is greater than thepitch of the second thread 374 a. Each of the first and second threads370 a, 374 a has a substantially uniform pitch.

Head portion 374 includes one or more slots 397 defined longitudinallytherethrough and extending proximally from a distal end of head portion374 through second thread 374 a. A plurality of splines 395 are disposedalong neck portion 375 and generally extend between a proximal end offirst thread 370 a and the longitudinal thickness of flange portion 390.Each slot 397 is configured to align with and receive a correspondingspline 395 to facilitate the mechanical coupling of head portion 374 tothe proximal end of shank 370. More specifically, flange portion 390 isdimensioned such that as splines 395 advance through a correspondingslot 397, a distal end of head portion 374 expands to accommodate flangeportion 390 therethrough and subsequently contracts circumferentiallyabout neck portion 375, e.g., in an interface-fit manner, tomechanically couple head portion 374 to the proximal end of shank 370,as best shown in FIG. 9B. To facilitate expanding of the distal end ofhead portion 374, one or more stress-relief fissures (not explicitlyshown) may be defined longitudinally through second thread 374 a (i.e.,parallel to slots 397). The independent head portion 374 configurationallows movement and/or rotation of the shank 370 about the “y” axis and“z” axis relative to the independent head portion 374 when the shank 370and head portion 374 are mechanically coupled, as shown in FIG. 9B.Further, the independent head portion 374 configuration inhibitsmovement and/or rotation of the about the “x” axis. More specifically,the interaction between splines 395 and corresponding slots 397 inhibitsmovement and/or rotation of shank 370 about the “x” axis. As headportion 374 is engaged by a screw driver (not shown) to cause rotationof bone screw 355 in a clock-wise and/or counter clock-wise direction,the slots 397 defined through second thread 374 a lockably engagecorresponding splines 395 disposed along neck portion 375 to cause shank370 to correspondingly rotate with head portion 374.

Bone screw 355 further includes a distal portion 380 that extendsproximally from the pointed tip portion 376. In one embodiment, distalportion 380 may be configured such that bone screw 355 is a“self-starting” or “self drilling” bone screw. In other embodiments,distal portion 380 may be configured such that bone screw 355 is a“self-tapping” bone screw as discussed above with respect to bone screw155. In either embodiment, distal portion 380 includes first and secondsidewalls 382, 384 that define a flute section 386. As best shown inFIG. 9B by way of example, the first and second sidewalls 382, 384 ofthe flute section 386 extend from the pointed tip portion 376 to a crest385 of thread 370 a near the distal end of shank 370. The first sidewall382 is planar and is aligned along a central longitudinal axis X′″-X′″of the bone screw 355 such that first sidewall 382 is coplanar with thecentral longitudinal axis X′″-X′″. As best shown in FIG. 9A by way ofexample, the second sidewall 384 further includes a planar portion 384 athat is parallel to the central longitudinal axis X′″-X′″ and an arcuateportion 384 b that extends proximally from the planar portion 384 a. Thearcuate portion 384 b is cut along a radius of curvature, as shown inFIG. 9A. Preferably, bone screws 355 are constructed of a material whichis harder than the material of the lips 190 b, 192 b, 194 b (FIG. 5) orlips 150 a, 152 a, 154 a (FIG. 6). For example, the bone screw may bemade of titanium alloy (e.g., Ti-6Al-4V) with the plate inserts or lipsmade of a softer compatible material, such as a softer titaniummaterial.

Referring now to FIGS. 10A and 10B, another embodiment of bone screw isshown referenced generally as 455. As described above with reference tobone screw 155, bone screw 455 is configured for use with spinalinterbody spacer 100 and/or spinal interbody spacer 200 in the samemanner as described hereinabove. Bone screw 455 includes a shank 470, aneck portion 475 extending between the shank 470 and a flange portion490 disposed at a proximal end of neck portion 475, an independenttapered head portion 474, and a pointed tip portion 476 at a distal endof the shank 470. The shank 470 has a uniform outer diameter and a firstcontinuous helical thread 470 a formed thereon for threaded insertioninto bone. A second continuous helical thread 474 a is formed on theindependent head portion for engaging lips 190 b, 192 b, 194 b (FIG. 5)or lips 150 a, 152 a, 154 a (FIG. 6). The pitch of the first thread 470a is greater than the pitch of the second thread 474 a. Each of thefirst and second threads 470 a, 474 a has a substantially uniform pitch.

Head portion 474 includes one or more stress-relief fissures 497 definedlongitudinally through second thread 474 a and extending proximally froma distal end of head portion 474. Stress-relief fissures 497 operate toexpand the distal end of head portion 474 to facilitate the mechanicalcoupling of head portion 474 to the proximal end of shank 470. Morespecifically, flange portion 490 is dimensioned such that as headportion 474 is mechanically coupled thereto, a distal end of headportion 474 expands to accommodate flange portion 490 therethrough andsubsequently contracts circumferentially about neck portion 475, e.g.,in an interface-fit manner, to mechanically couple head portion 474 tothe proximal end of shank 470, as best shown in FIG. 10B. Theindependent head portion 474 configuration allows poly-axial movement(e.g., about 10°) of the shank 470 relative to the independent headportion 474 when the shank 470 and head portion 474 are mechanicallycoupled, as shown in FIG. 10B. Also, shank 470 is rotatable about the xaxis.

Bone screw 455 further includes a distal portion 480 that extendsproximally from the pointed tip portion 476. In one embodiment, distalportion 480 may be configured such that bone screw 455 is a“self-starting” or “self drilling” bone screw. In other embodiments,distal portion 480 may be configured such that bone screw 455 is a“self-tapping” bone screw. In either embodiment, distal portion 480includes first and second sidewalls 482, 484 that define a flute section486. As best shown in FIG. 10B by way of example, the first and secondsidewalls 482, 484 of the flute section 486 extend from the pointed tipportion 476 to a crest 485 of thread 470 a near the distal end of shank470. The first sidewall 482 is planar and is aligned along a centrallongitudinal axis X″″-X″″ of the bone screw 455 such that first sidewall482 is coplanar with the central longitudinal axis X″″-X″″. As bestshown in FIG. 10A by way of example, the second sidewall 484 furtherincludes a planar portion 484 a that is parallel to the centrallongitudinal axis X″″-X″″ and an arcuate portion 484 b that extendsproximally from the planar portion 484 a. The arcuate portion 484 b iscut along a radius of curvature, as shown in FIG. 10A. Preferably, bonescrews 455 are constructed of a material which is harder than thematerial of the lips 190 b, 192 b, 194 b (FIG. 5) or lips 150 a, 152 a,154 a (FIG. 6). For example, the bone screw may be made of titaniumalloy (e.g., Ti-6Al-4V) with the plate inserts or lips made of a softercompatible material, such as a softer titanium material.

Spinal interbody spacer 100 will now be described for use with bonescrew 155. It should be understood that the following description isillustrative only in that spinal interbody spacer 100 or spinalinterbody spacer 200 may be adapted for use with any one or more of bonescrews 155, 255, 355, and 455. In the use of spinal interbody spacer100, the body 102 is inserted between adjacent vertebrae such thatprotrusions 122 of top and bottom vertebral engaging surfaces 112 a, 112b directly engage the surface of the adjacent vertebrae to preventspinal interbody spacer 100 from dislodging from between the adjacentvertebrae. Once the body 102 of spinal interbody spacer 100 is insertedbetween adjacent vertebrae, bone screws 155 are advanced through screwopenings 190 a, 192 a, 194 a and corresponding apertures 150, 152, 154toward hollow central region 134 such that self-starting portion 180engages the adjacent vertebrae to threadingly advance thread shank 170therein and anchor spinal interbody spacer 100 therebetween. As bestshown in FIGS. 4 and 5 and as discussed hereinabove, aperture 150 isangled in a first direction and apertures 152 and 154 are angled in asecond direction such that a bone screw 155 advanced through aperture150 is configured to anchor spinal interbody spacer 100 to one of theadjacent vertebrae and bone screws 155 advanced through apertures 152and 154 are configured to anchor spinal interbody spacer 100 to anotherof the adjacent vertebrae. As discussed hereinabove, as bone screw 155is advanced through any one of apertures 150, 152, 154 toward hollowcentral region 134, thread 174 a of head portion 174 engages thecorresponding lip 190 b, 192 b or 194 b to deform the lip and securebone screw 155 in the corresponding screw opening 190 a, 192 a or 194 asuch that bone screw 155 resists backing out of the screw opening.Further, head portion 174 of bone screw 155 is dimensioned to engagelips 190 b, 192 b, 194 b to prevent further advancement of bone screw155 toward hollow central region 134.

With returned reference to FIGS. 9A and 9B, the independent head portion374 configuration of bone screw 355 inhibits the backing out of bonescrew 355 from apertures 150, 152, 154 (FIG. 5) or apertures 250, 252,254 (FIG. 6). More specifically, the inhibition of movement and/orrotation of shank 370 about the “x” axis provided by the interactionbetween splines 395 and corresponding slots 397, inhibits correspondingrotation of head portion 374 about the “x” axis and, as a result,inhibits the dislodging and/or disengagement of the second thread 374 afrom lips 190 b, 192 b, 194 b (FIG. 5) or lips 150 a, 152 a, 154 a (FIG.6).

It can be understood from the foregoing disclosure of the exemplaryembodiment of spinal interbody spacer 100 that the spacer 100 provides aspinal implant that provides a desired amount of lordosis, and a desiredspacing between adjacent vertebral bodies, resists movement onceinserted, and provides a path for bone ingrowth.

It will be understood that various modifications may be made to theembodiments of the presently disclosed spinal interbody spacer.Therefore, the above description should not be construed as limiting,but merely as exemplifications of embodiments. Those skilled in the artwill envision other modifications within the scope and spirit of thepresent disclosure. By way of example only, the preferred embodimentincludes a PEEK interbody implant having titanium plate inserts to lockto the bone screws. It is contemplated that all or a portion of theimplant itself could be made of titanium with the lips that lockinglyengage the screws formed directly into the implant, rather than as aseparate insert as shown.

What is claimed is:
 1. A spinal spacer for engagement between vertebrae,comprising: a body having a first end surface at a distal end of thebody and a second end surface opposite thereto at a proximal end of thebody; the body extending between the first and second end surfaces todefine opposing top and bottom vertebral engaging surfaces substantiallysymmetrical about a centerline axis, the body further defining sidesurfaces; a hollow inner body defined by an opening extending throughthe top and bottom vertebral engaging surfaces; the second end surfaceof the body including at least one aperture formed therethrough at anangle relative to the centerline axis and in communication with thehollow inner body; a bone screw having a threaded screw shaft configuredand dimensioned to engage bone and a threaded screw head operablycoupled to a proximal end of the screw shaft such that the threadedscrew shaft is movable relative to the threaded screw head about atleast one axis; and at least one insert having a screw opening definedtherethrough and configured to be mounted to the body with the screwopening substantially aligned with the at least one aperture, the screwopening having a non-threaded lip formed therein, the non-threaded lipconfigured and dimensioned to engage the threads of the threaded screwhead of the bone screw inserted through the at least one aperture. 2.The spinal spacer of claim 1, wherein the hollow inner body is furtherdefined by an opening extending through the side surfaces.
 3. The spinalspacer of claim 1, wherein the insert is metallic.
 4. A spinal spacerfor engagement between vertebrae, comprising: a body having a first endsurface at a distal end of the body and a second end surface oppositethereto at a proximal end of the body, the body extending between thefirst and second end surfaces to define opposing top and bottomsurfaces, the body further defining side surfaces and a hollow opencentral region extending through the top and bottom vertebral engagingsurfaces, the second end surface of the body including at least oneaperture formed therethrough at an angle relative to a centerline axisextending between the proximal and distal surfaces, the at least oneaperture configured to receive an insert therein, the insert having ascrew opening defined therethrough and configured to align with the atleast one aperture, the screw opening having a non-threaded lip formedtherein, the non-threaded lip configured and dimensioned to engagethreads on a head of a screw inserted through the at least one aperture,the head of the screw operably coupled to a threaded screw shaft that ismovable relative to the head of the screw about at least one axis. 5.The spinal spacer of claim 4, further comprising a bone screw having ascrew head and a screw shaft, the screw shaft having a thread thereonconfigured and dimensioned to engage bone and the screw head havingthereon a screw thread configured and dimensioned to engage the lip ofthe screw opening.
 6. The spinal spacer of claim 5, wherein the insertis made of a titanium material and the bone screw is formed of atitanium alloy material which has a hardness greater than the titaniummaterial of the insert.
 7. The spinal spacer of claim 4, furthercomprising a bone screw having a screw head configured to operablycouple to a proximal end of a screw shaft, the screw shaft having athread thereon configured and dimensioned to engage bone and the screwhead having thereon a screw thread configured and dimensioned to engagethe lip of the screw opening.
 8. The spinal spacer of claim 7, whereinrotational movement of the screw head causes corresponding rotation ofthe screw shaft.
 9. The spinal spacer of claim 7, wherein the screw headincludes at least one slot defined therethrough configured to receive acorresponding spline disposed on the proximal end of the screw shaft tooperably couple the screw head to the screw shaft.
 10. The spinal spacerof claim 9, wherein rotation of the screw shaft about the x axis isinhibited.
 11. The spinal spacer of claim 9, wherein movement away fromthe hollow open central region of the bone screw within the at least onescrew opening is inhibited.
 12. The spinal spacer of claim 7, whereinthe screw head includes at least one stress-relief fissure definedtherein and configured to permit momentary expanding of a distal end ofthe screw head and subsequent contraction thereof about the proximal endof the screw shaft to operably couple the screw head to the proximal endof the screw shaft.
 13. The spinal spacer of claim 4, wherein the lipexists in a single plane that is substantially perpendicular to alongitudinal axis extending through the at least one aperture.
 14. Aspinal spacer for engagement between vertebrae, comprising: anon-metallic body having a first end surface at a distal end of the bodyand a second end surface opposite thereto at a proximal end of the body,the body extending between the first and second end surfaces to defineopposing top and bottom surfaces, the body further defining sidesurfaces and a hollow open central region extending through the top andbottom vertebral engaging surfaces, the second end surface of the bodyincluding at least one aperture formed therethrough, the at least oneaperture having a body screw opening defined therethrough, the bodyfurther including a plate cavity; and at least one metal insert havingan insert screw opening defined therethrough, the insert configured anddimensioned to be inserted into the plate cavity with the insert screwopening aligned with the body screw opening, the screw opening having anon-threaded lip formed therein, the non-threaded lip configured anddimensioned to engage threads on the head of a bone screw insertedthrough the at least one aperture, the head of the bone screw operablycoupled to a threaded screw shaft that is movable relative to the headof the bone screw about at least one axis.
 15. The spinal spaceraccording to claim 14, further comprising a bone screw having a screwhead and a screw shaft, the screw shaft having a thread thereonconfigured and dimensioned to engage bone and the screw head havingthereon a screw thread configured and dimensioned to engage the lip ofthe screw opening.
 16. The spinal spacer according to claim 15, whereinthe screw head is configured to operably couple to a proximal end of thescrew shaft.
 17. The spinal spacer of claim 15, wherein the metal insertis made of a titanium material and the bone screw is formed of atitanium alloy material which has a hardness greater than the titaniummaterial of the metal insert.
 18. The spinal spacer according to claim14, wherein the at least one aperture is at an angle relative to acenterline axis extending between the proximal and distal surfaces ofthe body.
 19. A method of fusing adjacent vertebrae, comprising:inserting a spinal spacer between the surfaces of the adjacentvertebrae, the spinal spacer extending between a first end surface at adistal end and a second end surface at a proximal end to define opposingtop and bottom surfaces substantially symmetrical about a centerlineaxis, the second end surface having at least one angled aperture definedtherethrough and at least one corresponding plate insert having a screwopening configured to substantially align with the at least one angledaperture; and advancing a bone screw through a first angled aperturedefined through the second end surface of the spinal spacer at a firstangle relative to the centerline axis and into the vertebrae until thebone screw engages bone and threads on the head of the bone screw engagea non-threaded lip formed in the screw opening to secure the bone screwrelative to the spinal spacer the head of the bone screw operablycoupled to a threaded screw shaft such that the threaded screw shaft ismovable relative to the head of the bone screw about at least one axis.20. The method of claim 19, wherein the second end surface includes atleast a second angled aperture defined therethrough and at least onecorresponding plate insert having a screw opening configured tosubstantially align with the at least one aperture.
 21. The method ofclaim 19, further comprising advancing a second bone screw through thesecond angled aperture.
 22. The method of claim 21, wherein the secondangled aperture is defined through the second end surface of the spinalspacer at a second angle relative to the centerline axis.
 23. A methodof fusing adjacent vertebrae, comprising: inserting a spinal spacerbetween the surfaces of the adjacent vertebrae, the spinal spacerextending between a first end surface at a distal end and a second endsurface at a proximal end to define opposing top and bottom surfacessubstantially symmetrical about a centerline axis, the second endsurface of the body including at least one aperture formed therethroughat an angle relative to a centerline axis extending between the proximaland distal surfaces, the at least one aperture having a metal insertdisposed therein, the metal insert having a screw opening definedtherethrough configured to align with the at least one aperture; andadvancing a bone screw through a first aperture defined through thesecond end surface of the spinal spacer at a first angle relative to thecenterline axis and into the vertebrae until the bone screw engages boneand threads on the head of the bone screw engages a non-threaded lipformed in the screw opening to secure the bone screw relative to thespinal spacer, the head of the bone screw operably coupled to a threadedscrew shaft that is movable relative to the head of the bone screw aboutat least one axis.
 24. The method of claim 23, wherein the second endsurface includes at least a second aperture defined therethrough and atleast one corresponding screw opening, the second aperture being definedat a second angle relative to the centerline axis.
 25. The method ofclaim 24, further comprising advancing a second bone screw through thesecond aperture.
 26. A spinal device comprising: a non-metallic bodyhaving an anterior wall, a posterior wall, and opposing side walls, theside walls extending between the anterior wall and the posterior wall;at least one opening extending through the body; an aperture disposed onthe posterior wall; and a metal insert having a screw opening, theinsert configured and dimensioned for placement within the aperture suchthat the screw opening is aligned with the at least one aperture, thescrew opening having a non-threaded lip formed therein, the non-threadedlip configured and dimensioned to engage threads on the head of a screwinserted through the aperture, the head of the screw operably coupled toa threaded screw shaft that is movable relative to the head of the screwabout at least one axis.
 27. The spinal device of claim 26, wherein theinsert is releasably positioned within the aperture.
 28. The spinaldevice of claim 26, wherein the body further includes a top surface anda bottom surface, the top and bottom surfaces having a plurality ofprotrusions extending therefrom.
 29. The spinal device of claim 28,wherein the at least one opening extends between the top and bottomsurfaces.
 30. A spinal spacer for engagement between vertebrae,comprising: a body having a first end surface at a distal end of thebody and a second end surface opposite thereto at a proximal end of thebody, the body extending between the first and second end surfaces todefine opposing top and bottom surfaces, the body further defining sidesurfaces and a hollow open central region extending through the top andbottom vertebral engaging surfaces, the second end surface of the bodyincluding at least one aperture formed therethrough at an angle relativeto a centerline axis extending between the proximal and distal surfaces,the at least one aperture having a screw opening defined therethrough,the screw opening having a lip formed therein; and a bone screw having ascrew head configured to operably couple to a proximal end of a screwshaft, the screw shaft having a thread thereon configured anddimensioned to engage bone and an outer surface of the screw head havingthereon a plurality of screw threads configured and dimensioned toengage the lip of the at least one aperture, wherein the screw headincludes at least one stress-relief fissure defined therein andconfigured to permit momentary expansion of a distal end of the screwhead and subsequent contraction thereof about the proximal end of thescrew shaft to operably couple the screw head to the proximal end of thescrew shaft.
 31. A spinal spacer for engagement between vertebrae,comprising: a body having a first end surface at a distal end of thebody and a second end surface opposite thereto at a proximal end of thebody, the body extending between the first and second end surfaces todefine opposing top and bottom surfaces, the body further defining sidesurfaces and a hollow open central region extending through the top andbottom vertebral engaging surfaces, the second end surface of the bodyincluding at least one aperture formed therethrough at an angle relativeto a centerline axis extending between the proximal and distal surfaces,the at least one aperture configured to receive an insert therein, theinsert having a screw opening defined therethrough and configured toalign with the at least one aperture, the screw opening having a lipformed therein, the lip configured and dimensioned to engage threads ona head of a screw inserted through the at least one aperture; and a bonescrew having a screw head configured to operably couple to a proximalend of a screw shaft, the screw shaft having a thread thereon configuredand dimensioned to engage bone and the screw head having thereon a screwthread configured and dimensioned to engage the lip of the screwopening, wherein the screw head includes at least one stress-relieffissure defined therein and configured to permit momentary expanding ofa distal end of the screw head and subsequent contraction thereof aboutthe proximal end of the screw shaft to operably couple the screw head tothe proximal end of the screw shaft.
 32. The spinal spacer of claim 31,wherein the lip exists in a single plane that is substantiallyperpendicular to a longitudinal axis extending through the at least oneaperture.
 33. A spinal spacer for engagement between vertebrae,comprising: a body having a first end surface at a distal end of thebody and a second end surface opposite thereto at a proximal end of thebody, the body extending between the first and second end surfaces todefine opposing top and bottom surfaces, the body further defining sidesurfaces and a hollow open central region extending through the top andbottom vertebral engaging surfaces, the second end surface of the bodyincluding at least one aperture formed therethrough at an angle relativeto a centerline axis extending between the proximal and distal surfaces,the at least one aperture having a screw opening defined therethrough,the screw opening having a non-threaded lip formed therein; and a bonescrew having a screw head configured to operably couple to a proximalend of a screw shaft such that the screw shaft is movable relative tothe screw head about at least one axis, the screw shaft having a threadthereon configured and dimensioned to engage bone and an outer surfaceof the screw head having thereon a screw thread configured anddimensioned to engage the non-threaded lip of the screw opening suchthat the thread on the outer surface of the screw head deforms thenon-threaded lip to secure the bone screw relative to the screw opening.34. The spinal spacer of claim 33, wherein the non-threaded lip is madeof a titanium material and the bone screw is formed of a titanium alloymaterial which has a hardness greater than the titanium material of thenon-threaded lip.